From: Michel Dänzer <michel.daenzer@xxxxxxx>
Fixes the BUG_ON spuriously triggering under the following
circumstances:
* ttm_eu_reserve_buffers processes a list containing multiple BOs using
the same reservation object, so it calls
reservation_object_reserve_shared with that reservation object once
for each such BO.
* In reservation_object_reserve_shared, old->shared_count ==
old->shared_max - 1, so obj->staged is freed in preparation of an
in-place update.
* ttm_eu_fence_buffer_objects calls reservation_object_add_shared_fence
once for each of the BOs above, always with the same fence.
* The first call adds the fence in the remaining free slot, after which
old->shared_count == old->shared_max.
In the next call to reservation_object_add_shared_fence, the BUG_ON
triggers. However, nothing bad would happen in
reservation_object_add_shared_inplace, since the fence is already in the
reservation object.
Prevent this by moving the BUG_ON to where an overflow would actually
happen (e.g. if a buggy caller didn't call
reservation_object_reserve_shared before).
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Michel Dänzer <michel.daenzer@xxxxxxx>
---
drivers/dma-buf/reservation.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
index 314eb1071cce..532545b9488e 100644
--- a/drivers/dma-buf/reservation.c
+++ b/drivers/dma-buf/reservation.c
@@ -141,6 +141,7 @@ reservation_object_add_shared_inplace(struct reservation_object *obj,
if (signaled) {
RCU_INIT_POINTER(fobj->shared[signaled_idx], fence);
} else {
+ BUG_ON(fobj->shared_count >= fobj->shared_max);
RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
fobj->shared_count++;
}
@@ -230,10 +231,9 @@ void reservation_object_add_shared_fence(struct reservation_object *obj,
old = reservation_object_get_list(obj);
obj->staged = NULL;
- if (!fobj) {
- BUG_ON(old->shared_count >= old->shared_max);
+ if (!fobj)
reservation_object_add_shared_inplace(obj, old, fence);
- } else
+ else
reservation_object_add_shared_replace(obj, old, fobj, fence);
}
EXPORT_SYMBOL(reservation_object_add_shared_fence);
--
2.18.0
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